[src/trunk]: src/usr.bin/make make(1): fix null pointer dereference when sys....

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/eb9b3b426a41
branches:  trunk
changeset: 937947:eb9b3b426a41
user:      rillig <rillig%NetBSD.org@localhost>
date:      Sat Aug 29 08:59:08 2020 +0000

description:
make(1): fix null pointer dereference when sys.mk is not found

This is quite hard to trigger in a real-life scenario since it requires
precise timing.

Instead, I created /tmp/sys.mk and ran "./make -m /tmp -f /dev/null" in
the debugger, after setting a breakpoint in this line:

ln = Lst_Find(sysMkPath, ReadMakefile, NULL);

Once this line was reached, I removed /tmp/sys.mk to make ReadMakefile
fail.  Just adding a few parse errors won't help since ReadMakefile only
fails if the file cannot be found.

diffstat:

 usr.bin/make/main.c |  8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diffs (36 lines):

diff -r e8c9419f894f -r eb9b3b426a41 usr.bin/make/main.c
--- a/usr.bin/make/main.c       Sat Aug 29 08:09:07 2020 +0000
+++ b/usr.bin/make/main.c       Sat Aug 29 08:59:08 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: main.c,v 1.323 2020/08/29 07:52:55 rillig Exp $        */
+/*     $NetBSD: main.c,v 1.324 2020/08/29 08:59:08 rillig Exp $        */
 
 /*
  * Copyright (c) 1988, 1989, 1990, 1993
@@ -69,7 +69,7 @@
  */
 
 #ifndef MAKE_NATIVE
-static char rcsid[] = "$NetBSD: main.c,v 1.323 2020/08/29 07:52:55 rillig Exp $";
+static char rcsid[] = "$NetBSD: main.c,v 1.324 2020/08/29 08:59:08 rillig Exp $";
 #else
 #include <sys/cdefs.h>
 #ifndef lint
@@ -81,7 +81,7 @@
 #if 0
 static char sccsid[] = "@(#)main.c     8.3 (Berkeley) 3/19/94";
 #else
-__RCSID("$NetBSD: main.c,v 1.323 2020/08/29 07:52:55 rillig Exp $");
+__RCSID("$NetBSD: main.c,v 1.324 2020/08/29 08:59:08 rillig Exp $");
 #endif
 #endif /* not lint */
 #endif
@@ -1329,7 +1329,7 @@
                ln = Lst_Find(sysMkPath, ReadMakefile, NULL);
                if (ln == NULL)
                        Fatal("%s: cannot open %s.", progname,
-                           (char *)Lst_Datum(ln));
+                           (char *)Lst_Datum(Lst_First(sysMkPath)));
        }
 
        if (!Lst_IsEmpty(makefiles)) {